Historically, various types of nonwoven webs have been utilized for use as disposable wet wipes. The various types of nonwovens used differ in visual and tactile properties, usually due to the particular production process used in their manufacture. In all cases, however, consumers of disposable wipes suitable for use as baby wipes demand strength, thickness, flexibility, texture and softness in addition to other functional attributes such as cleaning ability. Strength, thickness and flexibility can be correlated to certain measurable physical parameters, but perceived softness and texture are often more subjective in nature, and consumers often react to visual and tactile properties in their assessment of wet wipes. Optimizing all the desirable properties is often not possible. For example, often a balance of properties results in less than desirable softness or strength levels. Wet wipes used as baby wipes, for example, should be strong enough when wet to maintain integrity in use, but soft enough to give a pleasing and comfortable tactile sensation to the user(s). They should have fluid retention properties such that they remain wet during storage, and sufficient thickness, porosity, and texture to be effective in cleaning the soiled skin of a user. In addition, sufficient thickness and texture should be retained when wet after formation or combined with a lotion or composition to make a wipe.
Strength in a nonwoven web can be generated by a variety of known methods. If thermoplastic fibers are used, strength can be imparted by melting, either by through-air bonding or by hot roll calendaring. Adhesive bonding is also commonly used to bind fibers to increase the strength of the nonwoven. However, these processes, while increasing the strength of the nonwoven, generally detract from other desirable properties, such as softness and flexibility. Hydroentangling a fibrous structure generates nonwovens with high softness, flexibility and strength, but typically reduces the thickness of the material. Such a reduction in thickness is undesirable for many applications of nonwoven webs, such as in a wet wipe application. Due to the nature of cleaning tasks for which wet wipes are used, consumers prefer a wipe that has a high amount of apparent bulk, or thickness associated with it. To increase the basis weight of the starting material such that after hydroentangling the material retains sufficient thickness to be used as a baby wipe would be prohibitively expensive.
There, however, remains the need for a nonwoven web, which has the softness and flexibility associated with a hydroentangled nonwoven web, but retains the thickness lost in the hydroentangling process. There is also a need for a need for a nonwoven web which has the softness and flexibility associated with a hydroentangled nonwoven web and retains sufficient thickness and texture when wet after formation or combined with a lotion or composition to make a wipe. Similarly, there is also a need for a nonwoven web, which has the thickness associated with a through-air bonded or adhesive bonded nonwoven web, but retains the softness and flexibility lost in the through-air bonding or adhesive bonding processes.